html,body{
    height: 100%;
}
.tab {
    width:100%;
    height:0.8rem;
    font-size: 0.4rem;
    line-height: 0.8rem;
    display: flex;
    justify-content: space-around;
}
.tab div {
    width: 50%;
    text-align: center;
}
.check {
    background: #ccc;
}
.iframe{
    height: -webkit-calc(100% - 0.8rem);
    height:    -moz-calc(100% - 0.8rem);
    height:         calc(100% - 0.8rem);
}